If necessary, bake the sponge cake on a baking sheet.
Puree the strawberries. Mix the quark, sugar and grated lemon zest together. Add the strawberries.
Dissolve the gelatine (according to the instructions on the package!) And add to the quark mixture. Whip the cream with the cream stiffener + vanilla sugar until stiff and mix with the quark!
Spread the mixture on the cooled sponge cake and decorate with strawberries.
Chill for 3 hours in the refrigerator (or 1/2 hour in the freezer)!
It was an attempt and it turned out extremely well. Good Appetite!